Recently, tampons have been manufactured in such a way that an outer wrap is placed around an absorbent core. Wrappers have been utilized for a variety of purposes; among them, prevention of sloughing of individual fibers from the absorbent core during use, an insertion aid to provide a surface of lessened friction and a withdrawal aid. In the latter case, when superabsorbent material is present in the absorbent core of the tampon, a negative or suction pressure is developed along the surface of the tampon which tends to make the vaginal walls adhere to the outer surface and makes withdrawal uncomfortable.
Superabsorbent material has been considered particularly beneficial as an absorbent component in tampons because of its high absorbency per unit weight but the negative pressure developed by these materials has led to a series of attempts to provide an interfering or so-called "buffer" layer between superabsorbent material and the vagina. One such attempt is described in U.S. Pat. No. 3,999,549 in which a hydrophilic foam sheath surrounding a highly absorbent core is utilized to isolate the superabsorbent from the vagina. A similar concept by the same inventors is described in U.S. Pat. No. 4,020,841 with a subsidiary benefit set forth in both of these patents being the isolation of the absorbent material from vaginal contractions which would serve to prevent reverse fluid flow.
U.S. Pat. No. 3,683,912 discloses an absorbent tampon having an outer wrap of polypropylene fibers which is designed to reduce resistance to insertion.
Another patent concerned with difficulties inherent in the utilization of superabsorbent material as part of the absorptive component is U.S. Pat. No. 4,056,103. The tampon described therein embodies a wrapper which is a fluid permeable web with some measure of fluid retention capacity. The idea behind this invention is to ease withdrawal by providing a lubricated outer wrap obtained by fluid retention.
While the attempts to utilize an outer wrap to minimize the negative pressure encountered by the use of superabsorbent have been successful to some extent, the degree of success usually is accompanied by a concomitant decrease in the absorptive capabilities of the tampon. Absorptive capabilities in this context refer either to the rate of absorption, the outer wrap providing a barrier to some extent to the fluid uptake and/or to the amount of fluid absorbed. By their nature, tampons are restricted as to size and configuration and outer wraps or foam layers on the outside as described in U.S. Pat. No. 3,999,549 must replace needed absorptive volume with nonabsorptive or less absorptive volume in regard to the overall tampon construction. Also, while U.S. Pat. No. 3,999,549 describes the use of a foam outer layer to minimize the effect of vaginal contractions on the tampon, the foam layer itself would not be particularly advantageous to prevent reverse flow because the contractions would act to squeeze whatever menstrual exudate is within the interstices of the foam much like squeezing a sponge.
This invention provides a tampon which, not only is readily removable when a superabsorbent is used as part of the tampon absorbent material but this ease of removal can be retained without any noticeable decrease in absorption. In addition, reverse fluid flow, it is theorized, is substantially reduced when a tampon is made according to the teachings of this invention.